mirror of
https://github.com/libretro/scummvm.git
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131 lines
3.6 KiB
C++
131 lines
3.6 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* $URL$
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* $Id$
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*
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*/
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#include "common/endian.h"
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#include "cine/unpack.h"
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namespace Cine {
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uint32 CineUnpacker::readSource() {
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uint32 value = READ_BE_UINT32(_src);
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_src -= 4;
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return value;
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}
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int CineUnpacker::rcr(int inputCarry) {
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int outputCarry = (_chunk32b & 1);
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_chunk32b >>= 1;
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if (inputCarry) {
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_chunk32b |= 0x80000000;
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}
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return outputCarry;
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}
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int CineUnpacker::nextBit() {
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int carry = rcr(0);
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// Normally if the chunk becomes zero then the carry is one as
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// the end of chunk marker is always the last to be shifted out.
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if (_chunk32b == 0) {
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_chunk32b = readSource();
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_crc ^= _chunk32b;
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carry = rcr(1); // Put the end of chunk marker in the most significant bit
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}
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return carry;
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}
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uint16 CineUnpacker::getBits(byte numBits) {
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uint16 c = 0;
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while (numBits--) {
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c <<= 1;
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c |= nextBit();
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}
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return c;
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}
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void CineUnpacker::unpackRawBytes(uint16 numBytes) {
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_datasize -= numBytes;
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while (numBytes--) {
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*_dst = (byte)getBits(8);
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--_dst;
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}
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}
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void CineUnpacker::copyRelocatedBytes(uint16 offset, uint16 numBytes) {
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_datasize -= numBytes;
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while (numBytes--) {
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*_dst = *(_dst + offset);
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--_dst;
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}
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}
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bool CineUnpacker::unpack(byte *dst, const byte *src, int srcLen) {
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_src = src + srcLen - 4;
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_datasize = readSource(); // Unpacked length in bytes
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_dst = dst + _datasize - 1;
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_crc = readSource();
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_chunk32b = readSource();
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_crc ^= _chunk32b;
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do {
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/*
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Bits => Action:
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0 0 => unpackRawBytes(3 bits + 1) i.e. unpackRawBytes(1..9)
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1 1 1 => unpackRawBytes(8 bits + 9) i.e. unpackRawBytes(9..264)
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0 1 => copyRelocatedBytes(8 bits, 2) i.e. copyRelocatedBytes(0..255, 2)
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1 0 0 => copyRelocatedBytes(9 bits, 3) i.e. copyRelocatedBytes(0..511, 3)
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1 0 1 => copyRelocatedBytes(10 bits, 4) i.e. copyRelocatedBytes(0..1023, 4)
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1 1 0 => copyRelocatedBytes(12 bits, 8 bits + 1) i.e. copyRelocatedBytes(0..4095, 1..256)
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*/
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if (!nextBit()) { // 0...
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if (!nextBit()) { // 0 0
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uint16 numBytes = getBits(3) + 1;
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unpackRawBytes(numBytes);
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} else { // 0 1
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uint16 numBytes = 2;
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uint16 offset = getBits(8);
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copyRelocatedBytes(offset, numBytes);
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}
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} else { // 1...
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uint16 c = getBits(2);
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if (c == 3) { // 1 1 1
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uint16 numBytes = getBits(8) + 9;
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unpackRawBytes(numBytes);
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} else if (c < 2) { // 1 0 x
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uint16 numBytes = c + 3;
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uint16 offset = getBits(c + 9);
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copyRelocatedBytes(offset, numBytes);
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} else { // 1 1 0
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uint16 numBytes = getBits(8) + 1;
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uint16 offset = getBits(12);
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copyRelocatedBytes(offset, numBytes);
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}
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}
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} while (_datasize > 0 && _src >= src - 4);
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return _crc == 0;
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}
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} // End of namespace Cine
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